Guided bone regeneration around non-submerged implants in narrow alveolar ridges: a prospective long-term clinical study

Objectives: This prospective clinical study investigates long-term survival and clinical parameters of non-submerged implants with large buccal dehiscences treated with a deproteinized bovine bone mineral xenograft and a non-resorbable membrane in a one-stage approach. Material and methods: Sixteen consecutive non-submerged implants (ITI Straumann) were installed in narrow alveolar ridges in 13 patients (age range: 25-61 years). All patients were non-smokers. On the buccal site the bone dehiscence ranged between 3 and 9 mm. Primary stability was achieved in all but one implant. The exposed threads were covered with a xenograft (Bio-Oss((R))) and a non-resorbable expanded polytetrafluoroethylene membrane. The flap was sutured leaving the implant head non-submerged. The membrane was removed when (1) the membrane became exposed or (2) after a maximum of 24 weeks. All implants received singular cemented crowns. The implants were followed for a period ranging from 12 to 114 months. Whole-mouth plaque index (Pl), the % of bleeding on probing (BOP), probing depth and signs of peri-implantitis were recorded. Every year periapical radiographs were taken using a long cone technique. Results: All but one implant integrated successfully. At the time of membrane removal, all previously exposed threads were completely covered with richly vascularized tissue except for two implants where the coverage reached 63% and 87%, respectively. The whole-mouth plaque score and BOP remained low in all patients during the observation period. None of the implants had plaque and, except for one implant BOP never occurred. All implants were stable and in function. Swelling, redness or purulence was never observed. On the periapical radiographs no bone resorption was observed on the mesial and distal site except for one implant in one patient with a mesial and distal bone resorption of 2 and 3 mm. Probing depth was never higher than 3 mm except for one patient where the implant was placed deeply subgingival for esthetical reasons. Conclusion: This prospective long-term study shows that with the use of non-submerged transmucosal implants, large bony dehiscences can be treated in a one-stage approach using a stiff non-resorbable membrane combined with a xenograft.